ZBX-1946 added colspan/rowspan validation, but it is still possible to create wrong spans by removing rows or columns from a screen.

• create 2x2 screen
• in the upper left corner add element with colspan=2
• remove rightmost column, open element - colspan is still 2, and screen layout is broken
• change colspan to 1, rowspan to 2, go to screen list
• 'edit' for this screen, set rows to 1
• open screen, check element properties - rowspan is still 2, and screen layout is broken

when removing cols/rows, all spans should be checked & updated if necessary (pay attention to possibility of removing more than one col/row from screen properties !)